Chevrolet 10 1971 Series, Chassis Service Manual

Page: 184 / 466

ENGINE 6-6
VALVE
CLOSED POSITIVE L6 CLOSED POSITIVE V8
FLAME ARRESTOR
V A L V E
350 CU. IN. (RPO LS9)
& 402 CU. IN. (RPO L47)
X
\
307 CU. IN.
VALVE
Fig. 11— Crankcase Ventilation Systems
intake manifold destroys engine performance and
economy.
Service Fuel Lines and Fuel Filter
1. Inspect fuel lines for kinks, bends or leaks and cor­
rect any defects found. Refer to Section 8 for the
correct fabrication and replacement procedures for
fuel lines.
2. Inspect filter and replace if plugged.
NOTE:
If a complaint of poor high speed per-
Fig. 12— Crankcase Ventilation V a lv e
formance exists on the vehicle, fuel pump tests
described in Section 6M should be performed.
Service Cooling System
1. Inspect cooling system for leaks, weak hoses, loose
hose clamps and correct coolant level, and service
as required.
NOTE:
A cooling system pressure test, as de­
scribed in “ Additional Checks and Adjustments' ’
in this section, may be performed to detect
internal or external leaks within the cooling
system.
Service Crankcase Ventilation (Fig. 11)
All engines have a “ Closed Positive’’ ventilation sys­
tem utilizing manifold vacuum to draw fumes and con­
taminating vapors into the combustion chamber where
they are burned. Since it affects every part of the en­
gine, crankcase ventilation is an important function and
should be understood and serviced properly.
In a “ Closed Positive” ventilation system, air is
drawn through the engine crankcase (through a regulating
valve) (fig. 12) into the manifold, drawing crankcase
vapors and fumes with it to be burned. The “Closed
10-30 CHEVROLET TRUCK SERVICE MANUAL